Hi. I suffer from M.E./C.F.S, theres a few other regulars o here with fibro or M.E. Too so hopefully someone will be able to give you some advice.
Have you seen this thread? Its got alot of good stuff in it.
https://lovehoneyforum.com/t/disability-fun/262718
As ian said, there are also lots of old threads on here that might give you something too, so have a dig and you should find some stuff.
There have recently been quite a few threads about low libido, so you might get some good stuff there too. Ive been there, i know how difficult it is.
This thread has some really good ideas in it for no libido and i specifically liked this particular suggestion by @anon62893628 as its something i do myself and it can work really well.
Sadly i cant give any useful advice vis a vis the pain as i only get the fatigue with mine. Hopefully one of the more experienced guys on here will jump in later. Quite a few on here have arthritus and do make it work, so i would say, dont give up hope.
As for anal, i would start with buttplugs personally. Go slow, get something silicone and about 3.5 inches in circumference (make sure to read the sizes, it really matters for butt stuff). Get a good waterbased anal lube. I like sliquid sassy myself.
Theres a p,ethora of guides on the site, so having a read may help make it less scary.
Buttplug guides
Anal toy guides
If it helps, i never thought id be into anal, and discovered i really enjoy it. So you never really know untill you try.
If you want something less complex you can start with just a finger. Go to the loo and Have a good wash up before hand (good prep for any sort of anal play).
It can be strange at first, as your brain doesnt know how to process it. First couple of times i just had a “full” sort of feeling of pressure, but after doing it a few times it started feeling good.
Hope this was at least partially helpful and that you both find something that works for you. If youve got more questions, please ask. People are really helpful on here.